Self Assessment tax returns: who needs to file and key deadlines
Most employees never file a tax return, but self-employed people, landlords and others must. Who needs to file, the key deadlines and how to avoid penalties.
Most UK employees pay all their tax through PAYE and never need to file a tax return. But if you have income that is not taxed at source, or certain other circumstances apply, you must tell HMRC through Self Assessment. Missing the deadlines leads to penalties, so it pays to know whether it applies to you. This guide explains who needs to file a Self Assessment tax return, the key deadlines, payments on account, penalties and the move to Making Tax Digital.
Who needs to file a Self Assessment tax return
You usually need to file if you are self-employed as a sole trader with income over £1,000 in a tax year, a partner in a business partnership, or a landlord with rental income above the allowances. You may also need to file if you have untaxed income such as significant savings interest or dividends, foreign income, or capital gains to report. You also need to file if you or your partner receive Child Benefit and one of you has income above the High Income Child Benefit Charge threshold, unless you pay the charge another way. HMRC's online checker tells you if you need to file.
The £1,000 trading allowance and property allowance mean small amounts of side income, such as occasional selling or renting out a driveway, may not need to be reported at all.
Key Self Assessment deadlines
The tax year runs from 6 April to 5 April. If you need to file for the first time, you must register by 5 October after the end of the tax year. Paper returns are due by 31 October, and online returns by 31 January. Any tax owed is also due by 31 January. Filing online is simpler and gives you three more months. For the 2026/27 tax year, that means registering by 5 October 2027 and filing online by 31 January 2028.
Payments on account
If your Self Assessment bill is more than £1,000 and less than 80% of your tax is collected at source, you will usually have to make payments on account: two advance payments towards next year's bill, due on 31 January and 31 July. Each is normally half of the previous year's bill. Many people are caught out by this in their first year, when they owe the year's tax plus the first advance payment. For example, a first-year bill of £4,000 could mean paying £6,000 in January: £4,000 for the year plus a £2,000 payment on account. If your income falls, you can ask HMRC to reduce them.
Penalties for filing or paying late
Filing late brings an automatic £100 penalty, even if you owe no tax, with further penalties if you are later still, including daily penalties after three months. Paying late adds interest and late-payment penalties. If you cannot pay in full, you may be able to set up a payment plan with HMRC, which is far better than ignoring the bill.
Making Tax Digital for Income Tax
From April 2026, self-employed people and landlords with qualifying income over £50,000 must keep digital records and send quarterly updates to HMRC using compatible software, under Making Tax Digital for Income Tax. The threshold falls to £30,000 from April 2027 and £20,000 from April 2028. Choosing software early and keeping records as you go makes the change much easier.
Tips for a smooth tax return
Keep records of income and expenses throughout the year rather than gathering them in January. Claim allowable expenses, such as a share of home running costs if you work from home, business travel and equipment. Set aside a portion of self-employed income for tax in a separate savings account, ideally one that earns interest. Check our income tax and National Insurance guide for the current rates, and our guide to tax on savings interest if you have large savings.
Paying into a pension can reduce your tax bill; higher-rate taxpayers claim extra relief on personal pension contributions through Self Assessment. See our guide to the SIPP.
Frequently asked questions
When is the Self Assessment deadline?
31 January for online returns and payment, and 31 October for paper returns.
Do I need to file if I earn under £1,000 from self-employment?
Usually not, because of the £1,000 trading allowance.
What is the penalty for filing late?
An automatic £100, with further penalties the longer the return is late.
Sources
This article is general information, not financial advice.